Introduction

Medical management of nephrolithiasis is based on 24-hour urine collections (24U) despite limited evidence. We formed a multi-center collaboration to study medical management practices and outcomes in tertiary care stone centers. We hypothesize that those patients managed with dietary and/or pharmacotherapy with 24U will be less likely to recur than those managed without 24U.

Methods

Four centers collected data on recurrent calcium stone formers with at least 2 years of follow-up. Patients were placed in one of three groups based on recommendations given between initial presentation and first stone recurrence. Stone recurrences occurring within 6 weeks of initial presentation were censored. Groups were defined as diet, only given diet advice; medication, continuously recommended stone-specific pharmacotherapy; and hybrid, distinct periods of diet only and medication recommendations during follow-up. We compared the recurrence rates in these three groups overall and with regard to association with 24U.

Results

We collected data on 405 patients (58% male) with mean age of 49.9 ± 13.5 SD years and median BMI of 28.3 kg/m2 (IQR 25.1-32.9 kg/m2). Overall 297 (73.3%) patients had a stone recurrence during a median follow-up of 19.9 (range 8.4-36.6) months, with a median time to recurrence of 17.4 (7.6 – 33.2) months. Patients in the diet group (158/198, 80%) were more likely to recur compared to patients in the medication (38/54, 70% p= 0.13) or hybrid groups (101/153, 66% p< 0.004). Overall the majority of patients receiving medication recommendations during follow-up had 24U. Specifically, for the medication and hybrid groups, 79% and 95% respectively of those that recurred and 100% of those that did not recur had 24U collections. However, for the diet group overall fewer patients were managed with 24U (47%) compared to the medication (85%) and hybrid (97%) groups (p <0.0001). Furthermore, in the diet group significantly fewer patients had 24U in those that recurred (36%) compared to those that did not recur (90%) (p< 0.0001).

Conclusions

Overall recurrence rates were surprisingly high in our multi-center cohort, including for those given pharmacotherapy recommendations based on 24U. However, the highest recurrence rate and the poorest utilization of 24U was seen in those patients receiving diet recommendations only. While our results support 24U they demonstrate that risk stratification to portend severity of stone disease and response to treatment is needed.

Funding

None